The U.S. Food and Drug Administration (FDA) has issued a complete response letter (CRL) for Sanofi’s new drug application for tolebrutinib, aimed at treating non-relapsing secondary progressive multiple sclerosis (nrSPMS) in adults. 

On December 15, 2025, Sanofi updated investors on the ongoing review, revealing that the FDA now expects the review to extend beyond the previously announced revised U.S. target action date of December 28, 2025. The company added that “further guidance from the FDA [is] expected by the end of the first quarter of 2026” and confirmed that it had submitted an expanded access protocol for tolebrutinib in response to an FDA request. 

“Today’s FDA decision is a significant and meaningful change in direction from the feedback the agency previously provided to Sanofi. We are very disappointed by the FDA's action. Disability progression remains a large unmet medical need in MS, and tolebrutinib was previously awarded breakthrough therapy designation by the FDA in recognition of its potential to address this critical gap.  

"We believe that the FDA should also take the advice of scientific experts, clinicians, and patients in this matter to ensure all perspectives are considered. We remain committed to working with the FDA to find a path forward for tolebrutinib and ultimately serve the MS community,” said Houman Ashrafian, Executive Vice President and Head of Research & Development at Sanofi. 

Tolebrutinib had been provisionally approved in the United Arab Emirates in July 2025 for nrSPMS to slow disability accumulation independent of relapse activity. The drug is also under regulatory review in the European Union and other jurisdictions worldwide.